Re: CVS commit - JAMin 0.97.08

On Sat, 2007-06-30 at 23:16 -0700, R Parker wrote:
> --- Udo van den Heuvel <[email protected]> wrote:
> 
> > Jan Depner wrote:
> > >     *  Added per band delay to low and mid bands.
> > 
> > How do these delays work and what can I do with
> > them?
> > Anybody who can explain?
> 
> In live audio, when using old style P.A. gear which is
> probably anything that's not an line array, rooms
> greater than 120[ish] feet deep require delay lines.
> They are probably going to be hung between 50 and 70
> feet into the room. The delay line fills the back of
> the room with sound. You can imagine without the delay
> line the front of house (FOH) volume would have to be
> intolerably loud to fill the length of room.
> 
> Now consider what happens when FOH and the delay line
> produce same sounds at exactly the same time. FOH will
> reach the delay line after the line has produced the
> sound which creates an echo, slap or phasing.
> 
> To correct those issues the response of the delay line
> is held back until the FOH signal reaches the line and
> then it produces the same signals.
> 
> Mostly irrelevant is the fact that FOH and the delay
> line can be run at lower levels and the entire room is
> filled with sound.
> 
> Assuming high frequencies are slower than low and mid,
> it might prove prudent to delay them which presumably
> would eliminate phasing and cancelation. Obviously, we
> never hear echo or slapping in our studio playback
> systems.
> 
> The problem that's being addressed has never been
> demonstrated on this list. It is a mere proposal or
> developer curiousity. This software project has seen
> at least one other experimental concept that was
> eventually removed from the code. If nobody gets hurt,
> it's hard to say there's a problem. At the very least,
> the experiment is a learning experience. And maybe it
> becomes useful.
> 
> My advice is when you figure out how to use the band
> delays, be very mindful and listen carefully to what
> happens. I imagine; if minor adjustments fail to
> produce appreciable results, it's best to not adjust,
> at all. Afterall, our studio speaker runs are probably
> under 12 feet. Right?
> 

    That's very interesting but not the reason I wanted to add the
delays.  Here's a quote from BBE's site that explains what the delays
are meant to correct:

"When we listen to live music, all of the highs and lows reach our ears
in the same relationship to each other as when they were created by the
instruments. If this same live music were to be recorded and played back
through a loudspeaker system, the loudspeaker would introduce
frequency-dependent phase shifting. The inductance of the speaker's
voice coil creates a stronger impedance as the signal's frequency
increases, resulting in a time delay. Consequently, frequency components
with large negative phase shifts (high frequencies) arrive at the
listener's ear later than signals undergoing small phase shifts (low
frequencies). The resultant signal is distorted in the time domain to
the listener's ear. Audio material containing sharp transients (e.g.,
percussive and plucked sounds such as drums, guitar, piano and
harpsichord, etc.) suffers the most from this phenomenon, making it seem
unfocused, or mushy."

   When you mic all of the instruments at a gig you get the same delay
problems with the mains.  I use a BBE Sonic Maximizer to clean that up.
If you've never used a BBE Sonic Maximizer you should give them a try.
The first time I heard one in use was in Jimmy Jules' studio in Reserve,
LA.  I thought everything sounded just fine until he pushed the button
on the BBE.  The difference is pretty surprising.  Granted, the BBE has
a lot more going on than just the adjusted delay but that is a pretty
large part of it.


Jan


-- 
Jan 'Evil Twin' Depner
http://myweb.cableone.net/eviltwin69

"Life should NOT be a journey to the grave with the intention of 
arriving safely in an attractive and well preserved body, but rather to 
skid in sideways, chardonnay in one hand, chocolate in the other, body 
thoroughly used up, totally worn out, and screaming 'WOO HOO, what a ride'"


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